package com.itheima.test;

import java.util.ArrayList;

public class test {
    public static void main(String[] args) {
        ArrayList<Integer> list1 = new ArrayList<Integer>();
        ArrayList<Number> list2 = new ArrayList<Number>();
        ArrayList<Object> list3 = new ArrayList<Object>();

        show1(list3);
        show2(list1);
    }

    public static void show1(ArrayList<? super String> list) {

    }
    public static void show2(ArrayList<? extends Number> list) {

    }
}
